To go searching for cheap sex with wonderfully skanky sluts.
While this can often refer to "trolling" (aka taking whatever will follow) or tournament slutfishing (keeping the beauties, throwing back the trash).
Slutfishing is most common around the college campuses of America, although it is also a popular pastime in gyms, bars, whorehouses, massage parlors, restaurants, malls, streets, up in da club, the beach, the lake, deez nutz, the dump... okay, I was just kidding about the dump. You get the picture. You can pursue this activity in just about any bastion of freedom.

#1
Wendy: "I'm sorry I fucked your brother."
J: "If I had known that, I woulda been slutfishing when you were on the rag!"
Wendy: "Don't say that! You didn't mean that!"
J: "Okay, maybe I didn't. But I still would've motorboated your sister either way."

#2
Donny: "I'm bored. What should we do?"
Ralph: "Let's go to that club with that terrible DJ."
Donny: "Oh yeah! The music makes me want to puke raw shit out through my mouth, but the slutfishing there is excellent this time of night!"
Ralph: "We might as well. It's been a while since I've had the clap."

#3
Little Timmy: "Daddy? Are you going slutfishing with your friends tomorrow?"
Dad: "Yes son, we are."
Little Timmy: "What does that mean?"
Dad: "It means that we try to get knobjobs from any skank that's willing to give 'em."
Little Timmy: "What do you use for bait?"
Dad: "Well, here's what my grandpappy taught me... Carry a few extra bucks to buy Jager shots at the end of the night, and then whip out the Philly blunt to seal the deal. Also, having immediate access to pizza can help deter any fat, cockblocking friends."